I hope he's a companion. It's ironic that we don't know much about the Wardens despite playing as one in DA:O. Of course, it was an exceptional situation, and had Duncan lived he would have provided the necessary infodump.
There are so many points that can be played with that companion:
-What is the role of the Wardens in the Veil Tear crisis? They exist only to stop the Blights, but what happens if another end of the world is around the corner? Not a political crisis, but an honest End Of The World As We Know It. Shouldn't they help?
-Related to that, are they really neutral? Should they be? The Wardens who saved the world during the Blights (including our Warden) got their hands dirty in politics, if only to build massive alliances, but Alistair in DA2 (if he's a Warden) states that the rest of the Wardens didn't like it very much.
-The First Warden actually does politics, but the common Wardens aren't very imrpessed. The First Warden was the only who actually was delighted at the prospect of the Hero of Ferelden becoming Arl of Amaranthine. What if he/she tries to become King/Queen of the Anderfels?
-What did Avernus find out? Is it related to Coripheus being able to control Wardens and take over their bodies? What would happen if someone like Coripheus took control of the First Warden?
Questions, questions, and only that character could provide the answers we seek in Inquisition. If not, we would have to wait for the next game in the series portraying a Warden protagonist.
That picture with him walking away from the gallows is intriguing. What was his situation? A convicted saved in the last minute? An executioner sick and tired of his job?